Method of decolorizing a viscous mineral oil



Patented June 8, 1943 METHOD OF DECOLORIZENG A VISCOUS NINERAL OIL William s. chenauit, Weusviue, N. y., anla Albert E. Miller, Westfield, NK.,J., assignors to Sinclair Refining Company, New York, N. Y., a corporation of Maine Application September 20, 1939, Serial No.v 295,706

(Cl. 19E-147) 6 Claims.

This invention relates to the refining of mineral oils and, more particularly, to the decolorizing of mineral oils. The invention comprises an eicient and relatively inexpensive process for the continuous decolorization of viscous mineral oils with continuous recovery and reactivation of materials used in, and in connection with, the decolorization of such oils.

Numerous processes have been proposed heretofore and are now in commercial use in which mineral oils are subjected to the action of decolorizing earths. These processes require elevated temperatures in order to obtain efficient contact between oil and decolorizing earth, and many of these processes effect such contact in the presence of oxidizing atmospheres, such as air. These processes employing elevated temperatures of about 25o-650 F., and more commonly about 50o-650 F., whether conducted in an oxidizing atmosphere either intentionally or due vto the presence of adventitious air or air liberated from the grains of earth by the elevated temperature, cause oxidation of the treated oil and also elfect oxidation of coloring matter removed from the oil by the decolorizing earth. Oxidation of the treated oil is an obvious objection to these processes. Oxidation of the coloring matter removed from the oil vand adsorbed by the decolorizing earth usually prevents reactivation of the spent earth with solvents, and, in the few instances where reactivation of the spent earth may be accomplished with solvents, large and complex mixtures of expensive solvents are required, and even then the reactivated earth is not restored to its'original high decolorizing efficiency. Reactivation of spent decolorizing earth is necessary if such decolorizing processes are to be commercially feasible. Regeneration of spent earth by burning such earth to restore its decolorizing eiciency is accompanied by destruction of the grains of earth with the production of an excessive quantity of earth too ne for eflicient oil-earth separation.

We have discovered a novel process whereby mineral oils may be decolorized with decolorizing earths at relatively low temperatures with the advantages concomitant with such low temperature operation. Thus, the oil under treatment is not oxidized, even by the presence of adventitious oxygen or the like, and coloring matter removed fromthe oil by the decolorizing earth is not oxidized so that this coloring matter may be removed readily with suitable solvents to restore the original highdecolorizing efficiency of the earth.-

Our novel process for .decolorizing viscous mineral oils, and, more particularly, heavy petroleum oils, comprises subjecting such 'an oil diluted with a solvent therefor to the action of a decolorizing earth at a temperature not substantiallyin excess of about ,200 F. andreactivating the earthrseparated from the decolorized oil by subjecting it to the Iaction of aA solvent capable of extracting Afrom -the earth the coloring matter removed from the oil by said'earth. Both of these steps are particularly adapted to lcontinous operation. Qur process -is .characterized by the working-up of a slurry Aof theearth with the diluent prior to both the decolorizing andthe reactivating operations with attendant advantages hereinafter fully discussed.Y More specifically, the process of our invention comprises subjecting rthe oil diluted with a solvent therefor to the action of a decolorizing earth -at a tem'- perature -not substantially in excess of about 200 F., separating the earthfrom the decolorized oil, washing the -separated earth with -an additional quantity of said solvent to removeoil fromthe earth, reactivating the separated earth b'y subjecting it in the form of a slurry to the 'action of a solvent capable of extracting from the `e'arth the coloring matter removed `from the oil by said earth, separating the earth Afrom the color`solvent, Washing the separated reactivated e'a'r'th with an additional quantity ofthe first-menitioned solvent to remove the color solvent and coloring matter containedv therein', and returning the washed reactivated earth to the oil-decolorizing operation. The Washed reactivated yearth is advantageously Worked-up into a"l slurry with some of the solvent Aused in diluting the oil .before being returned to the oil-decolorizing operation. Each of the steps of our process may be conducted continuously with numerous advantages and economies which Will be readily apparent to one skilled in the art. Furthermore, each of the steps of our novel process may be carried out in an inert or substantially nonoxid-izing atmosphere. The process of our invent'ion is application to the decolori'zation of viscous, or heavy, mineral oils and, morel particularly, to viscous, or heavy, petroleum oils. The process may be used with particular advantage in the treatment of petroleum ylubricating oils either before or subsequent todevvaxin'g of such oils.

The oil to be treated is diluted Withnap'htlia inV our now-preferred operation although it must be understood that other oil solvents normallyfliquid at atmospheric pressure at the temperature employed and capable of dissolving the oil may be point of about 350 F. is particularly adapted for i use in our process. Commercial naphthas known as 200/300 or 30D/400 naphtha may also be used with advantage. The proportion of naphtha used in each instance will depend largely upon the viscosity of the oil to be treated. For example, from about 25% to about 150% naphtha by volume of oil to be treated may be used with oils ranging from low viscosity lubricating oils to high viscosity oils, respectively. We have found that the use of about 100% naphtha by volume of oil may be used with particular advantage for the treatment of a relatively high viscosity oil such, for example, as a dewaxed raflinate from a Pennsylvania cylinder stock. As a guidel to the amount of naphtha which may be used with advantage for various oils, we have found that enough naphtha should be used so that the blend of oil and naphthay will have a kinematic viscosity of about 4-6 centistokes at the temperature at which the spent decolorizin'g earth is separated from the mixture after decolorization contact. In general, we have found that efficient separation of spent earth from decolorized oil may be effected at temperatures of about 15G-200 F., although lower temperatures may be Vused with advantage.

A wide variety of pulverized, or finely divided,

decolorizing earths may be used in accordance with our invention. For example, finely divided fullers earth, activated bauxites such as Porocel, and acid-treated bentonites, such as Filtrol or Tonsil, may be used. We have found,

however, that the synthetic adsorbent decoloriz- 'y ingearth known' asl Magnesol may be used with particular advantage, this earth being highly eiiicient as a decolorizing agent at relatively low temperatures. Magnesol is a synthetic hydrated magnesium silicate normally obtained by rst preparing a hydrated calcium silicate and then reacting the calcium silicate with magnesium chloride.

We have found that contact between the diluted oil and the nely divided decolorizing earth may be carried out at temperatures of the order of about 12d-250 F., or better'150-200 F., and within this range we have found that temperatures between about' 150 F. and about 190 F. are particularly advantageous because of the low viscosity of'thevoil-naphtha blend and high efliciency of the decolorizing earth in this temperature range. i

We 'have investigated numerous solvents for the coloring material removed from the oil by the decolorizing earth and have found that the lower alcohols and ketones may be used with advantage. Thus, methyl, ethyl and isopropyl alcohols may be used eiectively, and such ketones as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone and dipropyl ketone'may be used advantageously. These solvents, either'alone or in combination, and in further admixture with naphtha, have been found to be particularly efficient in the process of our invention. A mixture of one part methyl ethyl ketone and twoparts naphtha may be used with particular advantage, although it must be understood that'other proportions of these and other above-noted solvents are sufciently powerful to be effective in our process. Each of the foregoing color solvents effects removal of coloring material from spent decolorizing earth in our process at temperatures ranging from atmospheric temperature to about 150 F., or somewhat higher. Wel

have found that salient and efficient results are obtained with a temperature of about F.

The process of our invention may be illustrated by reference to the accompanying schematic drawing in which, for the purpose of illustration, the oil to be decolorized vis diluted with Vnaphtha and spent earth is reactivated with a solvent mixture comprising one-third methyl ethyl ketone and two-thirds naphtha. Oil and naphtha are delivered continuously through the lines I and 2, respectively, in proper proportions into line 3 and heater i of the enclosed type where the oil diluted with naphtha is brought up to a temperature of about 15G-200 F. The diluted oil is then introduced through line 4 into a contact mix tank 5 of the enclosed type where it is thoroughly mixed with a slurry of decolorizing earth obtained either from storage, as when starting up our process, or from the reactivating step of our `process,during normal operation, as more fully described hereinafter. Continuous mixing and contact is provided by conventional mechanical stirring means assisted by recirculation from the bottom to the top of the tank by means of circulating pump 6. The mixture of decolorizing earth and diluted oil is delivered continuously to the primary de-oiling filter unit'l of the enclosed type which may comprise one or a plurality of rotary drum-type vacuum or pressure lters operated at a temperature ranging from atmospheric temperature to about 200 F., higher temperatures promoting higher solubilities of oil in naphtha and also higher filtering rates. Spent earth, containing coloring matter removed fi'om the oil, is continuously separated fromV the decolorized oil. The spent-earth cakel obtained in this filter unit is washed with naphtha obtained through line 8 preferably preheated to a temperature of about -200 F. in order to favor solubility of entrainedA oil in the wash naphtha. YThe primary filtrate from the filter unit, containing about QSE-99% of the total oil treated, is discharged through line 9 to a receiver I0 and comprises decolorized oil with the naphtha originally used as a diluent for the oil and, in addition, such naphtha as is required for the removal of a major proportion, say about 90%, of the oil normally contained in the spent-earth cake. This ltrate may then be subjected to any suitable stripping operation for the separation of'naphtha from the decolorized oil. Ifthe oil obtained from the stripping operation is slightly cloudy, it can be made brilliantly clear by subjecting it to Contact with a small amount of fresh decolorizing earth. The secondary filtrate from filter unit 1, comprising naphtha and a very small proportion of oil, is removed through line ll for return either to the primary filtrate in line 9 or, as now preferred, to the oil-naphtha blend being charged to the process through line 3, or b'oth. The spent-earth cake is continuously removed from the screen of the filter drum. The re,- moved cake, comprising approximately equal proportions of spent earth and naphtha, and also containing about 0.5-1.5% of the oil originally presentY in the cake before being washed, is then delivered continuously through a trough, or the like, indicated on the drawing as connection l2, into a Vslurry mix tank I3 of the enclosed type. Spent earth delivered to tank I3 is converted by conventional mixing means into a thick slurry either with fresh naphtha or, as now preferred, with the wash filtrate from the secondary lter, obtained as hereinafter described, in order later to obtain intimate contact between the spent The thick slurry of earth and color solvent. spent earth is delivered through line I4 toi extractor I5 of the enclosed type, provided with conventional mixing means, Where spent earth is reactivated by admixture with the color solvent comprising, in this example, a blend of methyl ethyl ketone and naphtha. The color solvent is preferably preheated to a temperature of about 130 F. before being mixed with the spent earth in extractor I5, in order to enhance the solubility of the coloring matter in the color solvent. The resulting slurry, containing about '2`5% earth by weight and comprising solvents and reactivated earth, is then passed through line I6 to the secondary, or reactivation, filter unit I'I of the enclosed type comprising one or more rotary drum-type vacuum or pressure filters maintained at an operating temperature ranging from atmospheric temperature to a moderate temperature of about 130 F., or as high as about 150 F., higher temperatures promoting higher filtering rates. The filter cake is washed with fresh naphtha supplied through line I8 preferably preheated to a temperature of about 130 F. Primary solvent filtrate from filter unit II consisting of a blend of naphtha and color solvent, together with a very small percentage of oil, is discharged through line I9 to a suitable solvent recovery unit. The last, or secondary, wash filtrate from unit I'I containing a small amount of color solvent is delivered by pump either through line 2| to primary solvent ltrate line I9 or, as now preferred, through line 22 to slurry mix tank I3 for use in working-up the slurry of spent earth as described hereinabove. Reactivated earth, formed as a cake on the screen drum of unit I'I and washed by naphtha introduced through line I8, is removed continuously from the drum and is conveyed, as indicated by connection 23, to slurry mix tank 24 of the enclosed type. The reactivated earth charged to tank 24 is Worked into a slurry with heated oil-naphtha blend drawn from line 4 by line 25, for example, or with naphtha obtained from line 2 or wash filtrate obtained from line I I, both as indicated by dotted lines 26 communicating with line 25. The resulting slurry of reactivated earth, obtained by conventional mixing means supplemented by pump 2'I and return line 28, is then delivered continuously through line 29 to contact mix tank 5 for reuse in the process of our invention. If, duiing normal operation. the slurry delivered to contact mix tank 5 through line 29 is made up With heated oil-naphtha blend drawn from line 4', and We now prefer this type of operation, all of the heated oil-naphtha blend dischargedfrom heater 4 into tank 5 is delivered first to slurry mix tank 24 and then introduced into tank E through line 29 instead of being discharged directly into tank 5 through line 4. The slurry thus delivered to contact mix tank 5 contains with advantage about 15-1'?% reactivated clay, on a dry basis, by Weight of the oil charged to our process. We have found that the decolorizing earth thus reactivated has substantially 100% efficiency.

All operations in our process employing elevated temperatures and carried out in apparatus of the enclosed type in which volatile solvents are present are provided, in accordance with our invention, with an atmosphere of an inert, or nonoxidizing, gas such, for example, as flue gas. This may be effected with particular advantage by providing two systems for supplying such inert atmospheres, one system including operations in which naphtha', or other oil solvent, is the only solvent present and a secondsystem including operations in which the color solvent is present. Each of theseV systems may be provided with appropriate foam traps, gas holders, heaters and* pumps adapted' to supply the inert gas continuously to the' operations as noted above. The inert gas circulated through each of these systems, in addition to preventing any re hazard occasioned by the presence of volatile solvent vapors admixed with adventitious air, is used with advantage for blowing filter cake from the drums of filter units 'I and I'I. This inert atmosphere is not necessary when the temperatures used in our process are sufficiently low to avoid any fire' hazard from inflammable mixtures of solvent vapors inasmuch as there is no substantial tendency toward oxidation of the oil and removed coloring matter at such low temperatures even in the presence of adventitious or other free oxygen, and the like.

In accordance with our invention contact between decolorizing earth and diluted oil sponsors efficient decolorization of the oil at relatively low temperatures. Dilution of the oil with naphtha permits intimate contact between the oil and the decolorizing earth and further facilitates removal of oil from theearth inasmuch as the diluted oil is more readily removed from the filter cake than is oil in undiluted form. Furthermore, the' use of a solvent such as naphtha permits the use of reactivated earth, wet with this solvent, Without requiring removal of the solvent and entrained moisture before reusing the reactivated earth. This represents a distinct advantage in the process of this type not only for the economy realized by the elimination of necessity of reducing reactivated earth to a dry condition but also because the elimination of such a drying operation prevents deterioration and breaking-down of the grains of decolorizing earth by elevated temperatures as is the case when reactivated earths are heated during conventional drying operations. Accordingly, the grains of decolorizing earth are not broken down in our process and as a result we have found that inexpensive drumtype filters maybe used effectively instead of the more expensive filtersv such, for example, as lprecoat type filters. Moreover, the absence of excessively fine grains of earth promotes high ltering rates and eliminates the necessity for guard filters which are required in conventional earth-contacting processes.

Inasmuch as all operations in the process of our invention are conducted at temperatures below the boiling point of water, there is no problempresented by the presence of entrained moisture. Furthermore, the use of relatively low ternperatures, and of inert atmospheres under certain conditions, in all operations employing these elevated, but relatively low, temperatures prevents oxidation of the oil so` that asphaltic substances, produced by oxidation of the oil, are not formed and do not clog the grains of earth in the filter cakes. The working-up of fresh and spent decolorizing earth into a slurry before the decolorizing and reactivating operations insures thorough and efcient contact between the earth and the oil and color solvent, respectively. The unoxidized condition of coloring matter adsorbed by the earth permits the removal, in accordance with our invention, with a smaller amount of color solvent than has been required heretofore.

Further economy is realized in the usel of oil solvents and color solvents inasmuch as ourv enclosed system permits complete recovery of these solvents, thus reducingthe losses which would otherwise occur. The enclosed system further provides assurance that no air, moisture, or other` disturbing influences can effect the results of the decolorizing step or the efficiency of the reactivated earth obtained in accordance with our invention. The fact that our process comprises a series of continuous operationsminimizes operation and labor costs.

We claim:

1. The method of decolorizing a viscous mineral oil which comprises subjecting the oil diluted with about 25-150% of naphtha by volume of the oil to the action of a decolorizing earth at a temperature not substantially in excess of about 200 F., separating the earth from the decolorized oil, reactivating the separated earth by subjecting it in the form of a slurry to the action of a color solvent capable of extracting from the earth the coloring matter removed from the oil by said earth, Washing the reactivated earth with naphtha to remove the color solvent and coloring matter contained therein, and returning the washed reactivated earth Wet with naphtha to the oil-decolorizing operation. f

2. The method of decolorizing a viscous mineral oil which comprises subjecting the oil diluted with a quantity of naphtha to the action of a decolorizing earth at a temperature not substantially in excess of about 200 F., the quantity of naphtha being such that the diluted oil has a kinematic viscosity of about 4-6 centistokes at a temperature of about 15G-200 F., separating the earth from the decolorized oil at a temperature not substantially in excess of about 200 F. and

such that the diluted oil will have a kinematic vis-- cosity of about 4-6 centistokes, reactivating the separatedearth by subjecting it in the form of a slurry to the action of al color solvent capable of extracting from the earth the coloring matter removed from the oil by said earth, Washing the reactivated earth with naphtha to remove the color solvent and coloring matter contained therein, and returning the washed reactivated earth wet With naphtha to theoil-decolorizing operation. v

3. The method of decolorizing a viscous mineral oilV which comprises subjecting the oil diluted with naphtha to the action of a decolorizing earth in a substantially non-oxidizing atmosphere at a temperature not substantially in excess of about 200 F., separating the earth from the decolorized oil, reactivating the separated earth by subjecting it in the form of a slurry to the action of a color solvent capable of extracting from the earth the coloring matter removed frorn the oil by said earth, Washing the reactivated earth With naphtha to remove the color solvent and coloring matter contained therein, and returning the Washed reactivated earth Wet with naphtha to the oil-dccolorizing operation.

4. The method of decolorizing a viscous mineral oil which comprises subjecting the oil di` luted with naphtha to the action of a decolorizing earth at a temperature not substantially in excess of about 200 F., separating the earth from the decolorized oil, washing the separated earth .with an additional quantity of naphtha to remove oil from the earth, reactivating the separated earth by subjecting it in the form of a slurry to the action of a color solvent capable of extracting from the earth the coloring matter removed from the oil by said earth, separating the earth from the color solvent, Washing the separated reactivated earth with an additional quantity of naphtha to remove the color solvent and coloring matter contained therein, and returning the washed reactivated earth Wet with naphtha to the oil-decolorizing operation.

5. The method of decolorizing a viscous mineral oil which comprises subjecting the oil diluted with naphtha to the action of a decolorizing earth in a substantially non-oxidizing atmosphere, continuously separating the earth from the decolorized oil at a temperature not substantially in excess of about 200 F. and such that the diluted oil will have a kinematic viscosity of about 4-6 centistokes, washing the separated earth with an additional quantity of naphtha to remove oil from the earth, reactivating the separated earth by subjecting it in the forni of a slurry to the action of a color solvent capable of extracting from the earth the coloring matter removed from the oil by said earth, separating the earth from the color solvent, Washing the separated reactivated earth with an additional quantity of naphtha to remove the color solvent and coloring matter contained therein, and returning the washed reactivated earth wet with naphthato the oil-decolorizing operation.

6. The method of decolorizing a viscous mineral oil which comprises continuously subjecting the oil diluted with naphtha to the action of a decolorizing earth at a temperature not substantially in excess of about 200 F., continuously separating the earth from the decolorized oil,

continuously Washing the separated earth Withv an additional quantity of naphtha to remove oil from the earth, continuously reactivating the separated earth by subjecting it in the form of a slurry to the action of a color solvent capable of extracting from the earth the coloring matter removed from the oil by said earth, continuously separating the earth from the color solvent, continuously washing the separated reactivated earth with an additional quantity of naphtha to remove the color solvent and coloring matter contained therein, and continuously returning the Washed reactivated earth wet with naphtha to the oil-decolorizing operation.

ALBER'I' E. MILLER. WILLIAM B. CHENAULT.

CERTIEICATE CE CORRECTION.

Patent No. 2,521,LI58. June 8, 19M.

WILLAM B. CHENAULT, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page l, second column, line im., for "applioation read --applioable--g page 5, second column, line T5, for the removal" read --its removal; and that the said.

Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. signed and sealed this 10th Cay of August, A. E. 19M.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

